Narco Guerra: Finding the Footage

We've all heard tales of terror from Mexico's drug wars and seen the pictures of the blood spilled on the streets. So it goes without saying that reporting on the "Narco Guerra" is dangerous. It can also be difficult to get to the facts.

Take the recent killing of drug cartel leader Antonio Ezequiel Cardenas Guillen, also known as "Tony Tormenta" or "Tony the Storm". His death – in an operation that reportedly included 150 marines, and was the result of more than six months intelligence work – saw frightened residents holed up in their homes. So how to find out how the sting actually happened?

Well, surprisingly you don't need an embed with the Mexican military, or a contact inside one of the cartels. The key to unlocking the clues: smart use of the internet.

On YouTube, CNN's Karl Penhaul found footage of the aftermath of the gun battle that killed Cardenas Guillen.

"This video offers us clues to the kind of weaponry that was involved. We can see that a huge hole has been blown up in a wall and the rest of the wall is heavily pockmarked. Now a private security source that works in that area that I have been talking to tells me almost certainly that 50 caliber heavy machine guns have been used here, and almost certainly two rocket-propelled grenades. We can certainly see from the images that this was not a surgical strike against the cartel but it was an absolutely slugfest, an out-and-out battle on the street of a city of half a million people just steps away from Brownsville, Texas".

According to Karl, Cardenas Guillen's death is "the equivalent of an earthquake in the narcosphere, and right now what is happening is that the tectonic plates of the drug underworld are shifting". A source tells him that a period of in-fighting between the gangs is expected, after which a new supreme leader will emerge.

As the drug turf wars continue, it's thought Reynosa could be the next target. In investigating that, information from blogs proves enlightening. There, frightened residents are using Twitter as a kind of early warning system, with neighbours letting each other know what's going on near them and offering support.

That's a crucial lifeline when traditional media are staying away from the area because of safety concerns.